Friction surfaced tool steel (H13) coatings on low carbon steel: A study on the effects of process parameters on coating characteristics and integrity

Tool steel H13 was friction surfaced on low carbon steel substrates. Mechtrode (consumable rod) rotational speed and substrate traverse speed were varied, keeping the axial force constant. The effects of process parameters on coating characteristics and integrity were evaluated. A process parameter window was developed for satisfactory deposition of tool steel coatings. Coating microstructures were examined using optical microscopy, scanning electron microscopy, and transmission electron microscopy. Microhardness tests, shear tests, and bend tests were conducted on coatings. The results show that coating width is a strong function of mechtrode rotational speed, while coating thickness is mainly dependent on substrate traverse speed. Lower mechtrode rotational speeds results in wider coatings, while higher substrate traverse speeds produce thinner coatings. Thinner coatings exhibit higher bond strength than thicker coatings. Coatings show no carbide particles, yet exhibit excellent hardness (above 600 HV) in as-deposited condition due to their martensitic microstructure.